1. Field of the Invention
This invention relates to telecommunications networks operating the Internet Protocol (IP), and relates especially to a method of reserving resources.
2. Description of Related Art
In third generation (3G) telecommunications networks, such as Universal Mobile Telecommunication System (UMTS), broad bandwidth is provided for services such as data and multimedia in addition to voice. An obvious need is that required Quality of Service (QoS) should be provided to users, but in IP networks, if contention for resources is not resolved, then QoS cannot be guaranteed.
In IP networks or the Internet in general, Resource reSerVation Protocol (RSVP) is used to allow the network to reserve resources so as to provide QoS. RSVP can be used for QoS control locally or it may be used across IP networks.
RSVP is an end-to-end protocol and is illustrated in FIG. 1. A transmitting user 10 sends to a receiving user 12 a message PATH. The PATH message carries the traffic characteristics information such as Tspecs to indicate the traffic behavior that is to be sent from the user 10. When the receiving user receives the PATH message, it sends a RESV message which contains QoS requests such as FlowSpecs. In practice, the transmitting and receiving users 10, 12 can be located remotely so that PATH and RESV messages pass through several nodes in UMTS. As each node receives either of the messages, it makes a decision as to whether adequate resources in that node can be reserved. If this is possible, then the messages are relayed to the next hop for the PATH message and to the previous hop for the RESV message. When the RESV message reaches the transmitting user 10, it begins to transmit data.
Periodic refresh messages are sent subsequently to maintain the QoS status at each node in which it has been set up.
At the TSG-SA Working Group 2 meeting No. 12 in Tokyo, 6-9, Mar. 2000 a disclosure was made by applicant of arrangements in which a mobile system using RSVP can communicate across a GPRS/UMTS network with another RSVP user; a proxy activated by the mobile receives and processes PATH messages and generates RESV messages in return.
Applicant's co-pending European published patent application no. EP-A-1154664 filed on even date describes an inventive method in which RSVP messages are filtered at a mobile and at a Serving GPRS Support Node (SGSN) or a Gateway GPRS Support Node (GGSN), and the mobile and the support node are arranged to activate Packet Data Protocol (PDP) Context Activation Procedure. However, conflicts can arise in certain circumstances.